This invention generally relates to a structural support for a hot gas duct and particularly relates to a novel construction of a support system for a modular heat exchanger of the type suitable as a steam generator for a steam power plant.
Power plants may include steam generators to produce motive fluid for driving steam turbines. One type of steam generator is known as a heat recovery steam generator (HRSG) and is employed in combined cycle power plants wherein hot exhaust gases from a gas turbine are passed in a non-contact heat exchange relation with feedwater to provide steam for a steam turbine thereby recovering otherwise wasted heat from the gas turbine exhaust.
The heat recovery steam generator may be made in sectionalized form by stacking modules, which include heat exchange tubes, one on top of the other to define a substantially vertical hot gas path. Fluid carrying tubes are disposed lengthwise across the heat exchange module and are supported by tube support plates. As the exhaust gas rises in the heat exchanger it loses heat in the heat exchange process. Similarly, as the feedwater passes downwardly in the hot exhaust gas path it turns to steam and then becomes superheated. Hence the heat exchange process is a counter-flow heat exchange process. Each sectional module is usually rectangular in form with the tube bundles running along the length of the rectangle. This provides maximum exposure of the tubes to the hot gas within the heat exchanger steam generator. Since the HRSG is of considerable length, lateral support is necessary along the length of the module to protect against wind loads and other forces which could cause lateral deformation.
One approach to lateral strengthening of the HRSG module is to provide cross members (relative to the gas flow path) attached at discrete points to the external sidewalls of the box. The sidewalls thus function as the lengthwise members. However, since the cross members must necessarily be located in the hot gas path in the type of construction under discussion the strengthening network would then consist of hot and cold members which would cause excessive lateral thermal deformation and/or locked in thermal loads. Lengthwise bracing of the exterior of the HRSG is likely to be insufficient unless tied to cross members. The problem thus presented is not believed to have found solution in the prior art.